The present invention relates to a gas valve. More particularly, it relates to a gas valve configured for back-to-back mounting with a second, similarly designed valve.
A variety of different gas-based heating equipment are available for use with various commercial/industrial applications. These appliances generally employ one or more gas burners, each supplied with liquefied petroleum (LP), natural or manufactured gas. Additionally, commercial/industrial gas heating equipment installations include one or more valves for controlling the flow of gas to the burner. In this regard, a number of different gas valve types exist, each having certain performance features and corresponding costs. For example, valves typically used in gas flow applications include diaphragm valves, solenoid valves, vent valves, shut-off valves, metering valves, butterfly valves, and fluid power valves, to name but a few.
While all of the above-identified valves are available for controlling gas flow, in many instances, a specific valve combination, or valve train, is required. As a point of reference, with most large scale commercial/industrial gas burning applications, the gas flow rate and consumption volume is very high. In light of the potential hazards associated with these applications, the Underwriters Laboratories Inc. (UL) has established valve train safety standards for commercial/industrial gas heating equipment. In particular, UL 795 sets forth the following valve requirements for mechanical-draft or atmospheric gas burners. For an installation having a gas burner input of 400,000 to 2,500,000 Btu/H (British thermal unit per hour), one valve rated for safety shut-off service (SSOV) is required. For installations having a gas burner input in the range of 2,500,000 to 5,000,000 Btu/H, two SSOV's in series, or one SSOV of the type incorporating a valve seal overtravel interlock, is required. For installations utilizing a gas burner input in the range of 5,000,000 to 12,500,500 Btu/H, two SSOV's in series, one of which incorporates a valve seal overtravel interlock, is required. Finally, for gas burner inputs in excess of 12,500,000 Btu/H, two SSOV's in series, one of which incorporates a valve seal overtravel interlock, is required. Further, for installations having burner inputs of 12,500,00 Btu/H or more, if the fuel gas has a specific gravity of less than 1.0, a normally open vent valve must be incorporated in line between the two SSOV's.
The above-provided UL code essentially dictates the required valve train configuration for most commercial/industrial gas burner applications. Pursuant to the UL code, then, many gas burner supply lines must include two safety shut-off valves mounted in series. Further, certain other applications require an additional vent valve disposed between the two safety shut-off valves. It should be noted that customers and/or installers may prefer to use two or more valves mounted in series for reasons other than UL code compliance. Currently, installation of two valves in series is relatively burdensome. Regardless of the exact valve type, virtually every gas valve includes a valve body defining an inlet port and an outlet port. Each of the inlet port and outlet port are internally threaded. Thus, in order to assemble two gas valves in series, a short length of appropriately sized pipe (or a "pipe nipple") must be formed and threaded. The pipe nipple is then threaded into the outlet port of the first valve and the inlet port of the second valve. Obviously, this labor intensive procedure is time consuming, and increases the overall length of the valve train. The mounting procedure is further complicated where a third valve, such as a vent valve, is necessary. An additional concern arises when one of the valves malfunctions. Replacement of the defective valve is cumbersome and therefore time-consuming. In short, current gas valve designs do not allow for a direct mounting of two gas valves back-to-back; instead, a pipe nipple must be used.
Recently, in response to the frequent installation requirement of two valves mounted in series and the associated difficulties of assembly, a singularly cast, two valve body design has been made available. The integrally casted, dual valve device does simplify the gas line assembly procedure in that it is no longer necessary to create and install a pipe nipple between the two valves. Unfortunately, however, certain other problems may arise. For example, the user is limited to the type of valve(s) formed in the single casted device. In other words, where the integrally casted, dual valve device incorporates two fluid power valves, the user is not able to replace one of the valves with a less expensive diaphragm valve. Additionally, if one of the continuous casting valves malfunctions, the entire assembly must be replaced even though the second valve may still operate properly.
Code requirements for industrial gas burning equipment require the use of two or more series mounted valves for many applications. The widely accepted practice of connecting the valves with pipe nipples is time-consuming and, therefore, expensive. Thus, a need exists for a gas valve configured to be readily mounted to a second valve in a back-to-back fashion.